1. Field of the Invention
The present invention relates to a semiconductor device to be applied for a radio communication device such as a mobile phone or the like, and also to a radio communication device using said semiconductor device.
2. Description of Related Art
FIG. 3 is a block diagram illustrating the electric arrangement of a mobile phone of which typical examples include a vehicle phone and a portable phone. An antenna 10 for transmitting and receiving a radio signal, is connected to a switch unit 1 for separating a transmission signal and a reception signal from each other. Connected to this switch unit 1 are a transmitter unit 2 and a receiver unit 3. A signal from a digital signal processing unit 5 (signal processing unit) is given to the transmitter unit 2 through a suitable filter circuit (not shown) after modulated by a modulator unit 4. A signal received by the receiver unit 3 is frequency-converted by mixers 6, 7, then filtered by band-pass filters 8, 9, then demodulated by a demodulator unit 11, and finally entered into the digital signal processing unit 5.
The transmitter unit 2 is formed by a gallium-arsenic compound semiconductor chip in which there are integrated (i) a mixer 21 for frequency-converting an intermediate-frequency signal corresponding to the contents to be transmitted, into a transmission-frequency signal, and (ii) an amplifying circuit 22 for amplifying an output signal of this mixer 21.
The receiver unit 3 is formed by a gallium-arsenic compound semiconductor chip in which there are integrated (i) an amplifying circuit 31 for amplifying a reception signal, (ii) a mixer 32 for converting, into a first intermediate-frequency signal, a reception-frequency signal supplied from a band-pass filter 12 for filtering an output signal of the amplifying circuit 31, and (iii) a local oscillator 33 for giving, to the mixer 32, a reference-frequency signal for frequency-conversion.
The mixers 6, 7 mix reference-frequency signals (of which phases are shifted from each other at the mixers 6, 7 by a phase shifter 14) from a local oscillator 13, with a first intermediate-frequency signal from the receiver unit 3. Thus, the mixers 6, 7 generate second intermediate-frequency signals lower in frequency than the first intermediate-frequency signal, and these second intermediate-frequency signals are entered into the demodulator unit 11 through band-pass filters 8, 9.
The modulator unit 4, the demodulator unit 11 and the digital signal processing unit 5 are arranged, for example, as integrated in a single silicon semiconductor chip.
Each of the band-pass filters 8, 9, 12 is formed by a surface acoustic wave (SAW) filter for processing a high-frequency signal favorably. The surface acoustic wave filter may be arranged by forming a comb-like electrode on the surface of a piezoelectric board made of ceramics and the like (alumina and the like).
The electric circuit of a mobile phone shown in FIG. 3 comprises a gallium-arsenic compound semiconductor chip forming the switch unit 1, a gallium-arsenic compound semiconductor chip forming the transmitter unit 2, a gallium-arsenic compound semiconductor chip forming the receiver unit 3, three silicon semiconductor chips respectively forming the band-pass filters 8, 9, 12, and a silicon semiconductor chip BC forming the modulator unit 4 and the like. These chips are bonded to one another on a printed circuit board by a flip-chip-bonding for example, thus forming the electric circuit of a mobile phone.
According to the arrangement above-mentioned, however, the inter-chip wiring lengths are inevitably long. This produces losses due to wiring reflection particularly at high-frequency processing units. To reduce such losses, matching circuits formed by microstrip filters and the like are interposed in the inter-chip wirings for impedance matching.
However, it is complicated to provide an arrangement for interposing such matching circuits in the inter-chip wirings. Further, microstrips should be formed on the board. This is disadvantageous in that the printed circuit board is inevitably increased in size to impede the miniaturization of a mobile phone. Although the use of the matching circuits can reduce the losses, the degree of loss reduction is not always satisfactory. Particularly in a portable phone of which power fully relies on the incorporated battery, the demand for reduction in power consumption is very high. Therefore, it is a matter of course that a further reduction in loss among the inter-chip wirings is desired.
If all the components can be integrated in a single semiconductor chip, the problem above-mentioned would be solved. However, it is difficult to form, by a silicon semiconductor, each of the switch unit 1, the transmitter unit 2, the receiver unit 3 and the like in which high-speed operation (800 MHz˜2 GHz:second frequency band) is required. On the other hand, it is not practical in view of process and cost to form, by a gallium-arsenic compound semiconductor chip, each of the modulator unit 4, the demodulator unit 11 and the like which are low-speed operational units (10˜200 MHz: first frequency band). Further, it is inevitable to form, as individual elements, the band-pass filters 8, 9, 12 each of which is formed by a surface acoustic wave filter. It is therefore not possible to integrate all the components in a single semiconductor chip.